What does everybody use as hold down clamps on their cnc plasma tables?

I could do with either some sort of low profile hold down clamp or maybe a stop to prevent lightweight or small sheets moving when the torch head collides with a part that hasn't fully dropped through the sheet!

I have several I've made, modeled on _Ogre's solution. They work great...as long as you have access to the bottom of your slats. As my table has filled up with debris, I find it's difficult to scrape out an opening on both sides for them to get under the slat.